The present invention relates generally to vacuum cleaners and more particularly to a vaneless impeller housing for a vacuum cleaner that increases operating efficiency and reduces noise attributable to air flow.
Efficient and quiet operation are important requirements for vacuum cleaners and similar air moving devices. To move the working fluid, i.e., air, within the vacuum cleaner an impeller is generally rotated within a housing by an electric motor. The impeller draws air at a central location and expels air about its circumference. The housing encloses the impeller and generally includes an air inlet passage located adjacent a central location on an inlet side of the impeller and a discharge passage extending about the circumference of the impeller.
It is known that some resistance to the free discharge of air from the impeller, or back pressure, increases its operating efficiency. Vanes are frequently provided disposed about the circumference of the impeller and within the discharge passage to provide back pressure. The vanes may have an involute configuration and are generally arranged to at least partially restrict the air flow. One disadvantage arising from the use of vanes in this manner is that they tend to generate noise. Air is a compressible fluid. As an impeller blade passes adjacent a leading edge of a vane the air is compressed and rapidly decompressed creating pressure pulses, i.e., noise. This noise is objectionable particularly in a vacuum cleaning device that may be used in a home or workshop.
Past proposals for eliminating or reducing noise include placing a dome structure over the housing into which the air is discharged. The large plenum created by the dome structure and the indirect pathway between the housing discharge passage and an air exit in the dome structure cooperate to reduce noise. Another proposal uses complex involute passages formed in the housing adjacent the circumference of the impeller. The involute passages are intended to provide smooth air flow and an increasing volume into which the discharge air decelerates to static pressure. These and other proposals, while offering varying degrees of success in maintaining impeller operating efficiency and reducing noise, have not been entirely satisfactory. Furthermore, a number of these proposals have added to the overall size of the impeller housing, and the complex involute passage proposal particularly adds to the manufacturing cost and complexity of the vacuum cleaner product.
In accordance with one aspect of the present invention, a vacuum cleaner includes a driven impeller that moves working air for the vacuum cleaner. A housing for the impeller has a first housing member including a first wall, a second housing member including a second wall opposite the first wall and an outlet for the working air. The impeller rotates and draws the working air through an opening and directs the working air radially outwardly toward the first wall and through a discharge passage formed between the first wall and the second wall. The discharge passage is annular and is substantially unobstructed. The discharge passage has a substantially constant width between the first wall and the second wall from its inlet to its outlet, which serves as a restriction on the working air to provide back pressure.
In accordance with a preferred form of the present invention, the working air is substantially unobstructed as it passes through the discharge passage, and the first and second housings are separate components. In addition, both the annular passage and the working air are unobstructed by vanes.
In accordance with another aspect of the present invention, a vacuum cleaner includes a driven impeller that moves the working air for the vacuum cleaner, a first housing including a first wall, a second housing including a second wall opposite the first wall, and wherein the first and second walls define an annular passage within an outlet passage for the working air. The impeller rotates and draws the working air through an opening and directs the working air radially outwardly toward the first wall and then through the annular passage. The annular passage is substantially uninterrupted about its full circumference. The annular passage may further define a minimum cross-section within the outlet.
In accordance with a further aspect of the present invention, a housing for an air impeller has a first housing and a second housing including a first wall and a second wall separated by a recess. The first housing and the first wall of the second housing define an annular passage for working air moved by the impeller. The annular passage is substantially uninterrupted about its full circumference.
In accordance with an even further aspect of the present invention, a vacuum cleaner includes a driven impeller that moves working air for the vacuum cleaner, a housing in which the impeller rotates, and an outlet for the working air. The housing has a first wall having an opening therein for admitting the working air, a second wall located generally radially outwardly from the impeller attached to the wall, a third wall attached to the second wall, a fourth wall opposite the first wall, and a fifth wall opposite the third wall and connected to the fourth wall. The fifth wall and the third wall form an annular passage that is substantially uninterrupted about a full circumference thereof.
Other features and advantages are inherent in the apparatus and methods claimed and disclosed or will become apparent to those skilled in the art from the following detailed description in conjunction with the accompanying drawings.